Former sports doctor Larry Nassar, left, stands with his attorney Shannon Smith as he pleads guilty to three counts of first-degree criminal sexual conduct.

DETROIT — Federal prosecutors on Thursday asked for a 60-year prison sentence for a Michigan sports doctor who was caught with child pornography while under investigation for sexually assaulting female gymnasts.

Larry Nassar, 54, who worked at Michigan State University and USA Gymnastics, will be sentenced for child porn crimes on Dec. 7. In the last week, he has pleaded guilty to molesting teens and younger girls with his hands in two other cases in state court.

Nassar "has led a double life," Assistant U.S. Attorney Sean Lewis said in a court filing. "On the surface, he was a respected, world-renowned expert for elite athletes. He was a medical doctor, a husband and a father. But underneath this veneer lurked a predator."

Lewis said Nassar "poses an immense risk to the community."

In July, he pleaded guilty to three charges in federal court in western Michigan, each carrying up to 20 years in prison. Sentences typically run at the same time, but U.S. District Judge Janet Neff can order separate, consecutive punishments.

Investigators found more than 37,000 images of child porn on Nassar's electronic devices. He acknowledged that he dumped computer hard drives in the trash and paid $49 to have a laptop's memory wiped clean to obstruct investigators who were hearing allegations about sexual assault.

The hard drives were discovered only because the trash truck in Nassar's neighborhood was late one day.

"To be clear, this defendant amassed an enormous collection of abominable images of children being sexually abused, raped and degraded," Lewis said.

Nassar pleaded guilty Wednesday to assaulting three girls at a Lansing-area gymnastics club while they sought treatment for injuries. He made a similar guilty plea last week, admitting that he molested girls at his Michigan State clinic and his home. Meanwhile, more than 100 women and girls are suing him.

Olympians Aly Raisman, McKayla Maroney and Gabby Douglas say they were victims when Nassar worked for Indianapolis-based USA Gymnastics.